linux-kernel - Re: [PATCH] driver core: bus: Fix a potential double free

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Message-ID: <20170831165708.GA26329@kroah.com>
Date:   Thu, 31 Aug 2017 18:57:08 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] driver core: bus: Fix a potential double free

On Tue, Aug 29, 2017 at 09:23:49PM +0200, Christophe JAILLET wrote:
> The .release function of driver_ktype is 'driver_release()'.
> This function frees the container_of this kobject.
> 
> So, this memory must not be freed explicitly in the error handling path of
> 'bus_add_driver()'. Otherwise a double free will occur.

Oh, nice catch!

> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> I have left the 'drv->p = NULL' even if it looks useless to me. It does not
> hurt. I have also left a comment to explain why we do not free 'drv->p'
> explicitly before zeroing this pointer.

We need that for when people do static structures.  Like as is done for
drivers.  Well, I think that's why we need it, can't really remember,
might as well be safe, the error handling paths here are crazy at
times...

thnaks,

greg k-h